[PATCHv3 1/6] ldbl-128ibm-compat: workaround GCC 9 C++ PR90731

[Tulio Magno Quites Machado Filho]

"Paul E. Murphy via Libc-alpha" <libc-alpha@sourceware.org> writes:

> GCC 9 has a bug (PR90731) whereby __typeof does not correctly copy
> exception specifiers[1].  Surprisingly, this can be quieted by declaring
> "#pragma system_header", or if the headers are installed in a system
> directory.
>
> Work around this by using the pragma for any gcc version between
> 9.0 and 9.2 to ensure tests continue to compile.
>
> [1] Example error from g++ 9.2.1:
>
> In file included from ../include/sys/cdefs.h:3,
>                  from ../include/features.h:465,
>                  from ../bits/libc-header-start.h:33,
>                  from ../math/math.h:27,
>                  from ../include/math.h:7,
>                  from test-math-isinff.cc:21:
> ../libio/bits/stdio-ldbl.h:25:20: error: declaration of ‘int sprintf(char*, const char*, ...)’ has a different exception specifier
>    25 | __LDBL_REDIR_DECL (sprintf)
>       |                    ^~~~~~~
> ../misc/sys/cdefs.h:461:26: note: in definition of macro ‘__LDBL_REDIR_DECL’
>   461 |   extern __typeof (name) name __asm (__ASMNAME ("__" #name "ieee128"));
>       |                          ^~~~
> In file included from ../include/stdio.h:5,
>                  from test-math-isinff.cc:22:
> ../libio/stdio.h:334:12: note: from previous declaration ‘int sprintf(char*, const char*, ...) throw ()’
>   334 | extern int sprintf (char *__restrict __s,
>       |            ^~~~~~~

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

-- 
Tulio Magno